This applet simulates the diffusion of particles after being released from a "box".
You can drag the box to change the starting position.

If the applet does not appear, please try the following:
(1) Download the Java software from www.java.com.
(2) Go to the menu: Tools > Turn off Pop-Up Blocker.
(3) Tools > Internet Options > Advanced > Security > Allow Active Contents.
(4) Start Menu > All Programs > Java > Configure Java > Security and then add this website to the Exception Site List.

Click here to download this page & the Java Class File.